On top of all the changes, my favorite part is NO LAG.
I'm having trouble getting used to everything running liquid-smooth like before ICS.
Battery life is excellent, I got a 2000mAh battery to combat ICS's problems, so no worries there.
Highlighting text works well again, my keyboard no longer lags or gets stuck, the screen follows the cursor while typing (one of the most annoying things about ICS).
I love that I can change the media and notification volume without going through Menu>Settings>Sound.

I haven't had any issues at all. Seems like I have a new device. Everything works fine and the new features are great. I would suggest updating thru Samsung website instead of kies. Seems like the people who have problems used kies

Thumbs up, for sure. Only gripe right now is that the clock app crashes whenever I try to set a new alarm. I've tried clearing data, force stop, reboots, but the problem persists. I didn't do a factory reset after the update, maybe that's the fix?

Tyndall, I haven't had either of those issues. In fact, my phone is charging away next to me as I type this and the red light is on. And yesterday, after a full charge, the blue light turned on. What I did notice though, is that the LED doe not stay on once you wake up the phone. As soon as the screen is off again though, the LED turns back on to the appropriate color.

LED only works when the screen is off, so if docked and displaying the clock, the LED will not light. At least that is my experience so far.

There is nothing major, but everything is better. The font changes and the way things work faster is great. I was sure I was going to upgrade the phone to a SIII, now won't do it until SIV come down in price. It does seem faster and I think I am getting better battery usage, but I am not a power user so wouldn't know and I take a spare battery every where I go. I don't like the monster batteries, makes the phone an anchor. I highly recommend updating if you haven't yet. I didn't have many problems updating with Kies, other than I deleted it and had to reinstall on Win7 64. Good luck to all.

Thumbs up, for sure. Only gripe right now is that the clock app crashes whenever I try to set a new alarm. I've tried clearing data, force stop, reboots, but the problem persists. I didn't do a factory reset after the update, maybe that's the fix?

I've had the same problem, except only when good to the clock through Beautiful Widgets (clicking on time on my home screen). If I go into the Clock app in the app drawer, it won't crash.

I'm very satisfied otherwise. Does anyone know if we got that Smart Stay feature like we were supposed to?

-The screen times out during video viewing on non-mobile sites
-Pwr+Home is a much harder key combo for me than Pwr+Vol Down, the new combo requires two hands to screenshot
-The new gallery is laggy and the buttons are inconvenient (they're in the menu rather than on the screen)
-Photo Editor is watered-down (I loved the old stretch/distort tool!)
-The widget that allows you to control brightness, screen timeout, Bluetooth, wifi, etc seems to no longer exist
-Some apps take hours to update, but end up failing anyway (not sure if this is JB's fault)
-THE SCREEN COMES ON WHEN YOU RECEIVE A TEXT! How was this remotely a good idea?! We have a red notification light for that, we dont need to waste battery on powering on the screen!!! > I wouldn't be pissed if they gave us the option to disable this.
-Because of the reason above, while texting the battery drains noticeably quicker (15% more over the course of a day)

Don't get me wrong, I love jelly bean, but some stuff was much better in ICS.

Still enjoying it, but decided to turn off Google Now, battery drain was a bit much.

I know... does Now NEED to know where it is all the time? I finally tracked down a means to toggle Google Location Services automatically... thing was throwing wakelocks like they were Mardi Gras beads... slowly sapping it dry while I thought it was sleeping. With that off, I can leave Now on and the drain is gone.

That was my only complaint with JB... some of the new apps were a little overzealous with their battery use when the screen was off. Outside of that, runs great and actually took care of some crashes I had in ICS.